The present disclosure relates generally to a plasma processing method using a plasma processing apparatus, and more particularly, to a plasma processing method including a step of plasma etching a processed substrate having a laminated structure including a magnetic film and a metal oxide film.
Dynamic random access memories (hereinafter referred to as DRAMs) and flash memories have conventionally been widely used in electronic devices and the like. These two types of memories, which differ in volatility (i.e., one is volatile, and the other is non-volatile), each suffer from its own disadvantages. A DRAM is a volatile memory, and is primarily used as a memory of a personal computer (hereinafter referred to simply as PC). Once the PC is shut off, data stored in the DRAM are lost.
In contrast, a flash memory is a non-volatile memory, and therefore shutting off a PC does not cause data stored in a flash memory to be lost semi-permanently. However, a data write operation on such a memory is very slow. Thus, use of a magnetoresistive random access memory (hereinafter referred to as MRAM), which is a non-volatile memory capable of overcoming these disadvantages, and at the same time, of achieving a high speed read operation, high capacity, low cost, and low power consumption, is desirable.
An MRAM utilizes a difference in electrical resistance associated with magnetization orientation directions of magnetic layers thereof. An MRAM requires a technique for processing at a fine scale by dry etching a magnetic film containing Fe, Co, Ni, and/or other elements, formed on a substrate using a masking material formed by lithography.
The technique of dry etching magnetic films can be either ion beam etching or plasma etching. Among these, plasma etching is widely used in the field of semiconductor device fabrication, and is more suitable for mass production due to uniformity of plasma etching of large diameter substrates.
Examples of a magnetic film etching technique using plasma etching include: a technique that utilizes formation of a chloride by Cl2 plasma formed by ionizing Cl2 gas; a technique that utilizes sputtering effect through ionization of Ar gas, which is an inert gas, or the like; and a technique that utilizes formation of a metal carbonyl by CO-containing plasma, formed by ionizing a mixture gas of CO gas and NH3 gas, or CO-containing gas such as CH3OH.
Among plasma cleaning methods, JP-A-2000-012515 discloses a cleaning method including steps of etching a laminated film formed of aluminum (Al) and titanium nitride (TiN), and thereafter using, as a cleaning gas, a gas mixture of boron trichloride (BCl3) gas and chlorine (Cl2) gas, or a gas mixture of boron trichloride (BCl3) gas and hydrogen chloride (HCl) gas, thereby to reduce the amount of deposit formed in the chamber to prevent formation of foreign matters.
JP-A-2002-359234 discloses a method including steps of removing metals, such as iron (Fe) and/or copper (Cu), adhered on an inner surface of a plasma processing chamber by plasma cleaning using fluorinated diketone gas, and thereafter removing an organic material adhered on the inner surface of the plasma processing chamber by oxygen (O2)-based plasma cleaning.
JP-A-2013-120810 discloses a method including steps of removing iron (Fe), nickel (Ni), and/or the like by a plasma cleaning technique using chlorine-containing gas, and thereafter removing the chlorine constituent remaining after the cleaning process from etching chamber by a plasma cleaning technique using hydrogen-containing gas, thereby to improve implantation of the chlorine constituent into a wafer having a magnetic film to reduce or eliminate corrosion on a wafer surface.